Technical Field
The invention relates to an apparatus for compacting fibrous plant material, in particular for compacting stalk material, having a feeding device for feeding the plant material or stalk material to be compacted, having at least one pair of press drums that are settable into opposite rotational movements, wherein one press drum has receiving grooves on its circumference along its axial longitudinal extent and another press drum has compression rings along its axial longitudinal extent, and having an internal cavity in at least one press drum, said internal cavity being connected to the receiving grooves via a multiplicity of radially oriented press channels that are distributed over the circumference.
Prior Art
The utilization of renewable raw materials, such as fibrous plant material, is increasingly gaining in importance. Thus, renewable raw materials, such as wood, but also harvested stalk material, for example straw, can be utilized further, for example for the purposes of bedding or combustion. In this case, it has proven very advantageous to pelletize such raw materials and to compact them to form pellets.
DE 20 2009 001 697 U1 discloses an apparatus for pressing pellets, which has a pair of press drums arranged downstream of a feeding device, said press drums rotating in opposite directions. One press drum has press channels that are open toward an internal cavity and which each have a receiving groove space in their upper region facing the circumference of the press drum. This receiving groove space is bounded by walls which comprise wall webs that are oriented in each case transversely to the direction of rotation of the press drums. The press drum having the press channels is assigned the other press drum which has compression rings with cylindrical press punches. During rotation of the press drums, each particular press punch passes into the associated press channel, on passing through or passing the connecting plane in which the rotation axes of the press drums are located, in order to plug the material to be pelletized into the press channel and form it into pellets. However, in this arrangement, it is the case that the wall webs, oriented transversely to the direction of rotation, of the walls of the press channel, including the wall regions bounding the groove receiving space, are at a distance from the circumferential surface of the compression ring, the press punches originating from said circumferential surface. As a consequence, the end sides of the wall webs, oriented transversely to the direction of rotation, of the receiving grooves act for their part as press devices and compact material located there against the circumferential surface of the compression ring, such that said material cannot pass into the press channels. In tough day-to-day operation, this results in the spaces between the press punches of the compression rings becoming clogged up, this not only resulting in increased reactive power of the apparatus but also in the risk of downtimes on account of clogging of the apparatus. Such clogging can only be remedied using very time-consuming and exhausting cleaning work.
U.S. Pat. No. 3,613,335 discloses an apparatus, to be towed by a towing vehicle, for pelletizing materials, said apparatus likewise having two press drums that are drivable in opposite directions. In order to gather the material to be pelletized from the ground, provision is made of a pick-up apparatus and a number of rotatable tine rolls which convey the material to be pelletized in the direction of a feeding device. The feeding conveying device consists of a conically configured drum that is drivable about an axis that is inclined with respect to the press drums, and also of a further drum which is arranged coaxially with a first press drum and is firmly connected thereto. This further drum runs in an internal recess of the conical drum that is arranged in an inclined manner. The material to be pelletized is thus moved via the coaxially arranged drum and an end-side face of the conical drum transversely to the direction of travel of the apparatus in the direction of a filling region between the press drums, and in the process is compacted to a small extent. A disadvantage with this apparatus is that, on account of lacking or insufficient counter-pressure, no effective compaction can take place. On account of the lateral feed of the material to be pressed, only very narrow press drums can be used for producing pellets. Thus, only a small throughput is achievable.
U.S. Pat. No. 2,052,449 discloses an apparatus for the continuous production of pellets from meltable starting materials which are intended to be suitable for subsequent consumption by for example animals or humans. To this end, provision is made of rolls having in each case an internal receiving space, into which material can be fed via press channels which are arranged in each case at a spacing apart from one another in the longitudinal direction of the rolls. Protrusions as compression rings are arranged, again in each case at a spacing apart from one another, between the press channels, said protrusions engaging in upper receiving spaces of the opposite roll, the press channels originating from said receiving spaces. However, the upper ends of the protrusions, which are configured in a planar manner, only dip into the receiving spaces to such an extent that a sufficient gap remains between the inlet of each particular press channel into its upper receiving space, in order to be able to allow the material to be compacted to be melted there. The creation of this melt is obligatory for the proper functioning of this machine, and so the latter is of little suitability for processing fibrous stalk material. An enormous amount of energy needs to be provided for melting the starting materials upstream of the respective press channels.
US 2010/0040721 A1 discloses a roller press for briquetting biomass. This press has two rolls that are drivable in opposite directions, said rolls having compression rings with intermediate grooves on their outer circumference. The compression rings of one roll engage in the grooves of the other roll. Distributed over the outer circumference of the compression rings are depressions which, together with the groove bottom of the grooves, form mold cavities for the briquettes to be produced. The pressing of the briquettes in depressions in the compression rings is limited in the known roller press.